Calculating Income Tax Evasion of Legal Entities and Examining its Sustainability through Threshold Non-linear Method

The purpose of this study is to calculate tax evasion based on the income of legal entities and to examine its stability, which has been done by estimating the Tanzi monetary demand function during 1370-1397. The demand function included the ratio of currency holdings to supply of money  as a dependent variable and the tax variables of legal entities, the ratio of wages and salaries to national income, real national per capita income, real interest rates paid on saving deposits and real oil revenues as independent variables. Then, the results used to estimate linear and nonlinear effect on tax evasion on the basis of income of legal entities by threshold regression during the period of study. The findings indicate a nonlinear model with significant coefficients, that the results are more satisfactory than the linear model and also  confirm the existence of a nonlinear relationship and fiscal instability in the income base of legal entities. The transition speed between the two regimes is equal to 3.20 according to the estimated transition parameter (git).That is the equations show that tax evasion changes will be strongly influenced by the  past tax evasion and will affect the behavior of this variable.